1. Field of the Invention
This invention relates to a propellant tank mounted on, for example a spacecraft such as an artificial satellite to store a liquid propellant and supply vapor produced by evaporation of part of the liquid propellant to an external location, and a vapor jet emitting device for producing thrust by emitting a jet of the vapor supplied from the propellant tank.
2. Description of the Related Art
A propellant tank of this type constituting the prior art is disclosed in Japanese Patent Application Preliminary Publication No. 2009-214695, for example.
The propellant tank disclosed therein comprises a tank body for storing a liquid propellant, foamed metal filling approximately the whole interior of the tank body, and a heater surrounding the tank body. The tank body has a gas outlet. The tank body stores the liquid propellant in a state that the liquid propellant is held in pores of the foamed metal.
This propellant tank is designed to cause evaporation of part of the propellant in the tank body by heating with the heater. A vapor jet emitting device including this propellant tank is designed to supply vapor produced inside the tank body, to a thruster connected to the gas outlet so that the thruster can produce thrust by emitting a vapor jet.
The aforementioned prior-art propellant tank with weighty foamed metal filling approximately the whole interior of the tank body can store the liquid propellant in a state that it is held in pores of the foamed metal, but cannot be lightweight.
Further, the aforementioned prior-art propellant tank requires that heat be transferred to the whole mass of the foamed metal by heating with the heater in order to cause evaporation of part of the propellant, and thus, requires a much greater amount of external thermal energy than otherwise. These are the problems with the prior art to which a solution is sought.